/*
 * This file is part of WebLookAndFeel library.
 *
 * WebLookAndFeel library is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * WebLookAndFeel library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with WebLookAndFeel library.  If not, see <http://www.gnu.org/licenses/>.
 */

package com.alee.graphics.image.gif;

/*
 * NeuQuant Neural-Net Quantization Algorithm
 *
 * Copyright (c) 1994 Anthony Dekker
 *
 * NEUQUANT Neural-Net quantization algorithm by Anthony Dekker, 1994. See
 * "Kohonen neural networks for optimal colour quantization" in "Network:
 * Computation in Neural Systems" Vol. 5 (1994) pp 351-367. for a discussion of
 * the algorithm.
 *
 * Any party obtaining a copy of these files from the author, directly or
 * indirectly, is granted, free of charge, a full and unrestricted irrevocable,
 * world-wide, paid up, royalty-free, nonexclusive right and license to deal in
 * this software and documentation files (the "Software"), including without
 * limitation the rights to use, copy, modify, merge, publish, distribute,
 * sublicense, and/or sell copies of the Software, and to permit persons who
 * receive copies from any such party to do so, with the only requirement being
 * that this copyright notice remain intact.
 *
 * @author K Weiner
 */
@SuppressWarnings ( "JavaDoc" )
public class NeuQuant
{
    protected static final int netsize = 256; /* number of colours used */

    /* four primes near 500 - assume no image has a length so large */
    /* that it is divisible by all four primes */
    protected static final int prime1 = 499;

    protected static final int prime2 = 491;

    protected static final int prime3 = 487;

    protected static final int prime4 = 503;

    protected static final int minpicturebytes = 3 * prime4;

    /* minimum size for input image */

    /*
     * Program Skeleton ---------------- [select samplefac in range 1..30] [read
     * image from input file] pic = (unsigned char*) malloc(3*width*height);
     * initnet(pic,3*width*height,samplefac); learn(); unbiasnet(); [write output
     * image header, using writecolourmap(f)] inxbuild(); write output image using
     * inxsearch(b,g,r)
     */

    /*
     * Network Definitions -------------------
     */

    protected static final int maxnetpos = netsize - 1;

    protected static final int netbiasshift = 4; /* bias for colour values */

    protected static final int ncycles = 100; /* no. of learning cycles */

    /* defs for freq and bias */
    protected static final int intbiasshift = 16; /* bias for fractions */

    protected static final int intbias = 1 << intbiasshift;

    protected static final int gammashift = 10; /* gamma = 1024 */

    protected static final int gamma = 1 << gammashift;

    protected static final int betashift = 10;

    protected static final int beta = intbias >> betashift; /* beta = 1/1024 */

    protected static final int betagamma = intbias;

    /* defs for decreasing radius factor */
    protected static final int initrad = netsize >> 3; /*
     * for 256 cols, radius
     * starts
     */

    protected static final int radiusbiasshift = 6; /* at 32.0 biased by 6 bits */

    protected static final int radiusbias = 1 << radiusbiasshift;

    protected static final int initradius = initrad * radiusbias; /*
     * and
     * decreases
     * by a
     */

    protected static final int radiusdec = 30; /* factor of 1/30 each cycle */

    /* defs for decreasing alpha factor */
    protected static final int alphabiasshift = 10; /* alpha starts at 1.0 */

    protected static final int initalpha = 1 << alphabiasshift;

    protected int alphadec; /* biased by 10 bits */

    /* radbias and alpharadbias used for radpower calculation */
    protected static final int radbiasshift = 8;

    protected static final int radbias = 1 << radbiasshift;

    protected static final int alpharadbshift = alphabiasshift + radbiasshift;

    protected static final int alpharadbias = 1 << alpharadbshift;

    /*
     * Types and Global Variables --------------------------
     */

    protected byte[] thepicture; /* the input image itself */

    protected int lengthcount; /* lengthcount = H*W*3 */

    protected int samplefac; /* sampling factor 1..30 */

    // typedef int pixel[4]; /* BGRc */
    protected int[][] network; /* the network itself - [netsize][4] */

    protected int[] netindex = new int[ 256 ];

    /* for network lookup - really 256 */

    protected int[] bias = new int[ netsize ];

    /* bias and freq arrays for learning */
    protected int[] freq = new int[ netsize ];

    protected int[] radpower = new int[ initrad ];

    /* radpower for precomputation */

    /*
     * Initialise network in range (0,0,0) to (255,255,255) and set parameters
     * -----------------------------------------------------------------------
     */

    public NeuQuant ( final byte[] thepic, final int len, final int sample )
    {

        int i;
        int[] p;

        thepicture = thepic;
        lengthcount = len;
        samplefac = sample;

        network = new int[ netsize ][];
        for ( i = 0; i < netsize; i++ )
        {
            network[ i ] = new int[ 4 ];
            p = network[ i ];
            p[ 0 ] = p[ 1 ] = p[ 2 ] = ( i << netbiasshift + 8 ) / netsize;
            freq[ i ] = intbias / netsize; /* 1/netsize */
            bias[ i ] = 0;
        }
    }

    public byte[] colorMap ()
    {
        final byte[] map = new byte[ 3 * netsize ];
        final int[] index = new int[ netsize ];
        for ( int i = 0; i < netsize; i++ )
        {
            index[ network[ i ][ 3 ] ] = i;
        }
        int k = 0;
        for ( int i = 0; i < netsize; i++ )
        {
            final int j = index[ i ];
            map[ k++ ] = ( byte ) network[ j ][ 0 ];
            map[ k++ ] = ( byte ) network[ j ][ 1 ];
            map[ k++ ] = ( byte ) network[ j ][ 2 ];
        }
        return map;
    }

    /*
     * Insertion sort of network and building of netindex[0..255] (to do after
     * unbias)
     * -------------------------------------------------------------------------------
     */

    public void inxbuild ()
    {

        int i, j, smallpos, smallval;
        int[] p;
        int[] q;
        int previouscol, startpos;

        previouscol = 0;
        startpos = 0;
        for ( i = 0; i < netsize; i++ )
        {
            p = network[ i ];
            smallpos = i;
            smallval = p[ 1 ]; /* index on g */
            /* find smallest in i..netsize-1 */
            for ( j = i + 1; j < netsize; j++ )
            {
                q = network[ j ];
                if ( q[ 1 ] < smallval )
                { /* index on g */
                    smallpos = j;
                    smallval = q[ 1 ]; /* index on g */
                }
            }
            q = network[ smallpos ];
            /* swap p (i) and q (smallpos) entries */
            if ( i != smallpos )
            {
                j = q[ 0 ];
                q[ 0 ] = p[ 0 ];
                p[ 0 ] = j;
                j = q[ 1 ];
                q[ 1 ] = p[ 1 ];
                p[ 1 ] = j;
                j = q[ 2 ];
                q[ 2 ] = p[ 2 ];
                p[ 2 ] = j;
                j = q[ 3 ];
                q[ 3 ] = p[ 3 ];
                p[ 3 ] = j;
            }
            /* smallval entry is now in position i */
            if ( smallval != previouscol )
            {
                netindex[ previouscol ] = startpos + i >> 1;
                for ( j = previouscol + 1; j < smallval; j++ )
                {
                    netindex[ j ] = i;
                }
                previouscol = smallval;
                startpos = i;
            }
        }
        netindex[ previouscol ] = startpos + maxnetpos >> 1;
        for ( j = previouscol + 1; j < 256; j++ )
        {
            netindex[ j ] = maxnetpos; /* really 256 */
        }
    }

    /*
     * Main Learning Loop ------------------
     */

    public void learn ()
    {

        int i, j, b, g, r;
        int radius;
        int rad;
        int alpha;
        final int step;
        int delta;
        final int samplepixels;
        final byte[] p;
        int pix;
        final int lim;

        if ( lengthcount < minpicturebytes )
        {
            samplefac = 1;
        }
        alphadec = 30 + ( samplefac - 1 ) / 3;
        p = thepicture;
        pix = 0;
        lim = lengthcount;
        samplepixels = lengthcount / ( 3 * samplefac );
        delta = samplepixels / ncycles;
        alpha = initalpha;
        radius = initradius;

        rad = radius >> radiusbiasshift;
        if ( rad <= 1 )
        {
            rad = 0;
        }
        for ( i = 0; i < rad; i++ )
        {
            radpower[ i ] = alpha * ( ( rad * rad - i * i ) * radbias / ( rad * rad ) );
        }

        // fprintf(stderr,"beginning 1D learning: initial radius=%d\n", rad);

        if ( lengthcount < minpicturebytes )
        {
            step = 3;
        }
        else if ( lengthcount % prime1 != 0 )
        {
            step = 3 * prime1;
        }
        else
        {
            if ( lengthcount % prime2 != 0 )
            {
                step = 3 * prime2;
            }
            else
            {
                if ( lengthcount % prime3 != 0 )
                {
                    step = 3 * prime3;
                }
                else
                {
                    step = 3 * prime4;
                }
            }
        }

        i = 0;
        while ( i < samplepixels )
        {
            b = ( p[ pix ] & 0xff ) << netbiasshift;
            g = ( p[ pix + 1 ] & 0xff ) << netbiasshift;
            r = ( p[ pix + 2 ] & 0xff ) << netbiasshift;
            j = contest ( b, g, r );

            altersingle ( alpha, j, b, g, r );
            if ( rad != 0 )
            {
                alterneigh ( rad, j, b, g, r ); /* alter neighbours */
            }

            pix += step;
            if ( pix >= lim )
            {
                pix -= lengthcount;
            }

            i++;
            if ( delta == 0 )
            {
                delta = 1;
            }
            if ( i % delta == 0 )
            {
                alpha -= alpha / alphadec;
                radius -= radius / radiusdec;
                rad = radius >> radiusbiasshift;
                if ( rad <= 1 )
                {
                    rad = 0;
                }
                for ( j = 0; j < rad; j++ )
                {
                    radpower[ j ] = alpha * ( ( rad * rad - j * j ) * radbias / ( rad * rad ) );
                }
            }
        }
        // fprintf(stderr,"finished 1D learning: final alpha=%f
        // !\n",((float)alpha)/initalpha);
    }

    /*
     * Search for BGR values 0..255 (after net is unbiased) and return colour
     * index
     * ----------------------------------------------------------------------------
     */

    public int map ( final int b, final int g, final int r )
    {

        int i, j, dist, a, bestd;
        int[] p;
        int best;

        bestd = 1000; /* biggest possible dist is 256*3 */
        best = -1;
        i = netindex[ g ]; /* index on g */
        j = i - 1; /* start at netindex[g] and work outwards */

        while ( i < netsize || j >= 0 )
        {
            if ( i < netsize )
            {
                p = network[ i ];
                dist = p[ 1 ] - g; /* inx key */
                if ( dist >= bestd )
                {
                    i = netsize; /* stop iter */
                }
                else
                {
                    i++;
                    if ( dist < 0 )
                    {
                        dist = -dist;
                    }
                    a = p[ 0 ] - b;
                    if ( a < 0 )
                    {
                        a = -a;
                    }
                    dist += a;
                    if ( dist < bestd )
                    {
                        a = p[ 2 ] - r;
                        if ( a < 0 )
                        {
                            a = -a;
                        }
                        dist += a;
                        if ( dist < bestd )
                        {
                            bestd = dist;
                            best = p[ 3 ];
                        }
                    }
                }
            }
            if ( j >= 0 )
            {
                p = network[ j ];
                dist = g - p[ 1 ]; /* inx key - reverse dif */
                if ( dist >= bestd )
                {
                    j = -1; /* stop iter */
                }
                else
                {
                    j--;
                    if ( dist < 0 )
                    {
                        dist = -dist;
                    }
                    a = p[ 0 ] - b;
                    if ( a < 0 )
                    {
                        a = -a;
                    }
                    dist += a;
                    if ( dist < bestd )
                    {
                        a = p[ 2 ] - r;
                        if ( a < 0 )
                        {
                            a = -a;
                        }
                        dist += a;
                        if ( dist < bestd )
                        {
                            bestd = dist;
                            best = p[ 3 ];
                        }
                    }
                }
            }
        }
        return best;
    }

    public byte[] process ()
    {
        learn ();
        unbiasnet ();
        inxbuild ();
        return colorMap ();
    }

    /*
     * Unbias network to give byte values 0..255 and record position i to prepare
     * for sort
     * -----------------------------------------------------------------------------------
     */

    public void unbiasnet ()
    {

        int i;

        for ( i = 0; i < netsize; i++ )
        {
            network[ i ][ 0 ] >>= netbiasshift;
            network[ i ][ 1 ] >>= netbiasshift;
            network[ i ][ 2 ] >>= netbiasshift;
            network[ i ][ 3 ] = i; /* record colour no */
        }
    }

    /*
     * Move adjacent neurons by precomputed alpha*(1-((i-j)^2/[r]^2)) in
     * radpower[|i-j|]
     * ---------------------------------------------------------------------------------
     */

    protected void alterneigh ( final int rad, final int i, final int b, final int g, final int r )
    {

        int j, k, lo, hi, a, m;
        int[] p;

        lo = i - rad;
        if ( lo < -1 )
        {
            lo = -1;
        }
        hi = i + rad;
        if ( hi > netsize )
        {
            hi = netsize;
        }

        j = i + 1;
        k = i - 1;
        m = 1;
        while ( j < hi || k > lo )
        {
            a = radpower[ m++ ];
            if ( j < hi )
            {
                p = network[ j++ ];
                try
                {
                    p[ 0 ] -= a * ( p[ 0 ] - b ) / alpharadbias;
                    p[ 1 ] -= a * ( p[ 1 ] - g ) / alpharadbias;
                    p[ 2 ] -= a * ( p[ 2 ] - r ) / alpharadbias;
                }
                catch ( final Exception ignored )
                {
                } // prevents 1.3 miscompilation
            }
            if ( k > lo )
            {
                p = network[ k-- ];
                try
                {
                    p[ 0 ] -= a * ( p[ 0 ] - b ) / alpharadbias;
                    p[ 1 ] -= a * ( p[ 1 ] - g ) / alpharadbias;
                    p[ 2 ] -= a * ( p[ 2 ] - r ) / alpharadbias;
                }
                catch ( final Exception ignored )
                {
                }
            }
        }
    }

    /*
     * Move neuron i towards biased (b,g,r) by factor alpha
     * ----------------------------------------------------
     */

    protected void altersingle ( final int alpha, final int i, final int b, final int g, final int r )
    {

        /* alter hit neuron */
        final int[] n = network[ i ];
        n[ 0 ] -= alpha * ( n[ 0 ] - b ) / initalpha;
        n[ 1 ] -= alpha * ( n[ 1 ] - g ) / initalpha;
        n[ 2 ] -= alpha * ( n[ 2 ] - r ) / initalpha;
    }

    /*
     * Search for biased BGR values ----------------------------
     */

    protected int contest ( final int b, final int g, final int r )
    {

        /* finds closest neuron (min dist) and updates freq */
        /* finds best neuron (min dist-bias) and returns position */
        /* for frequently chosen neurons, freq[i] is high and bias[i] is negative */
        /* bias[i] = gamma*((1/netsize)-freq[i]) */

        int i, dist, a, biasdist, betafreq;
        int bestpos, bestbiaspos, bestd, bestbiasd;
        int[] n;

        //noinspection NumericOverflow
        bestd = ~( 1 << 31 );
        bestbiasd = bestd;
        bestpos = -1;
        bestbiaspos = bestpos;

        for ( i = 0; i < netsize; i++ )
        {
            n = network[ i ];
            dist = n[ 0 ] - b;
            if ( dist < 0 )
            {
                dist = -dist;
            }
            a = n[ 1 ] - g;
            if ( a < 0 )
            {
                a = -a;
            }
            dist += a;
            a = n[ 2 ] - r;
            if ( a < 0 )
            {
                a = -a;
            }
            dist += a;
            if ( dist < bestd )
            {
                bestd = dist;
                bestpos = i;
            }
            biasdist = dist - ( bias[ i ] >> intbiasshift - netbiasshift );
            if ( biasdist < bestbiasd )
            {
                bestbiasd = biasdist;
                bestbiaspos = i;
            }
            betafreq = freq[ i ] >> betashift;
            freq[ i ] -= betafreq;
            bias[ i ] += betafreq << gammashift;
        }
        freq[ bestpos ] += beta;
        bias[ bestpos ] -= betagamma;
        return bestbiaspos;
    }
}